Multicarrier Channel Equalization and Crosstalk Cancellation
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Solution Overview
Problem
Existing digital communication systems face challenges in efficiently performing channel equalization and far-end crosstalk cancellation in multicarrier data transmission systems, particularly due to the complexity and slow convergence of current methods, as well as the need for additional hardware and restrictions on frequency usage.
Innovation Solution
The implementation of a multicarrier data transmission system that concurrently trains and updates coefficients for channel equalization and far-end crosstalk cancellation using a FFT unit, adaptive channel equalizer, and FEXT unit, allowing for joint adaptive determination of coefficients and shared resources for both far-end and near-end crosstalk purposes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time-domain channel estimation techniques are used to estimate channel impulse response, then the channel can be estimated for far-end or near-end noise cancellation and equalization, but the solution produces only a single error signal that is used to update all taps of a finite impulse response filter, resulting in complex implementation and slow convergence
Solution Approach 1:
The patent divides the channel estimation problem into frequency-domain sub-problems by processing individual DMT tones separately. Each tone's channel response is estimated independently using frequency-domain adaptive comb filter techniques, avoiding the need to update all FIR filter taps simultaneously with a single error signal. This segmentation enables parallel processing and faster convergence while reducing implementation complexity.
Solution Approach 2:
The patent replaces time-domain mechanical filter updating with frequency-domain computational methods. Instead of using a finite impulse response filter that requires sequential tap updates, the system uses frequency-domain adaptive comb filters that operate on individual DMT tones, substituting the mechanical filtering approach with computational signal processing that converges faster and is easier to implement.
2Productivity
If frequency-domain channel identification approaches are used with fast Fourier transforms, then each tap can be independently trained and adapted, but additional hardware for fast Fourier transforms and inverse fast Fourier transforms is required on the receiver side
Solution Approach 1:
The patent makes the existing DMT modulation framework perform dual functions: data transmission and channel estimation. The same IFFT/FFT operations used for DMT signal generation and detection are also utilized for channel estimation, eliminating the need for separate dedicated hardware. The frequency-domain adaptive comb filter taps are trained using the same frequency-domain processing already present in the DMT system, achieving multi-functionality without additional hardware overhead.
3Measurement precision
If training signals span the entire frequency bandwidth for frequency-domain channel estimation, then complete channel response can be obtained, but restrictions on usage of certain frequencies prevent utilization of the entire frequency bandwidth
Solution Approach 1:
The patent accepts that channel estimation will be performed using only the subset of frequencies permitted for training, rather than attempting to use the entire frequency bandwidth. The frequency-domain adaptive comb filter is trained on the available training frequencies, and the channel response is estimated accurately for those frequencies. This partial action approach works within the system constraints while still achieving effective channel equalization for the usable bandwidth.
Data Source
AI summary
Improved techniques for concurrent channel equalization and far-end crosstalk channel compensation (e.g., estimation and/or cancellation) in a multicarrier data transmission system are disclosed. The improved techniques can produce coefficients for an electronic filter that provide channel equalization and for an electronic filter that provides cancellation of the far-end crosstalk. These coefficients can be initially trained and then subsequently updated during data transmission. Optionally, common coefficient determination resources can be utilized for both far-end crosstalk and near-end crosstalk purposes. These improved techniques are particularly suitable for use with a digital multicarrier communication system having multiple-input multiple-output systems.